Marine Mammal Facts: Gray Whale (Eschrichtius robustus)

The gray whale (Eschrichtius robustus) was once known as the Devil Fish because of its fierce hunting methods and its ability to overturn boats when they feel threatened. However, the gray whale isn't a fish at all. It must surface for air to breathe just like other marine mammals.

Quick Facts on Gray Whales

Scientific name:Eschrichtius robustus

Type of whale: Baleen

Average length: 46 feet (females are larger than males)

Average weight: 30 - 40 tons

Gestation: 12 - 13 months

Life span: 50-77 years

Habitat and Range: Pacific Ocean, Northern Atlantic, and Arctic Ocean

Diet: crab, shrimp, lobsters, barnacles, squid, fish, and plankton

IUCN status: overall listed of least concern, but western gray whales are listed as critically endangered

Appearance

As you might have guessed, this whale gets its name from the coloring of its body. It is gray in color with white spots. Many times you will see barnacles and several scratches along the body. Sometimes you will even see spots of orange, but this is due to whale lice. Gray whales have long, streamlined bodies that taper and narrow at the head. The upper jaw is arched and slightly overlaps the lower jaw. On the ventral jaw, lower jaw, there are two to five grooves that are approximately five feet in length.

The gray whale does not have a dorsal fin, but instead it is more of a dorsal hump located two-thirds the way down its back. Located right behind the dorsal hump is six to twelve dorsal knuckles. It also has paddle shaped flippers that come to a point at the end. Its fluke, or tail fin, can reach ten to fifteen feet. These whales can grow to lengths of 46 feet and weighing in at 30 to 40 tons. The female are typically larger than the males.

Being a baleen whale, it has a approximately 130-180 fringed overlapping plates hanging from each side of the upper jaw, where teeth would normally be located. These plates consist of a keratin that fray out into fine hairs inside the mouth close to the tongue. These plates are off-white in color and about two to ten inches in length.

They have layer of blubber that is approximately ten inches thick to keep them warm in frigid water temperatures. They also have hairy bristles, called vibrissae, located on their snout that acts as tactile sensors.

Source

Life Cycle

Gray whales typically reach sexual maturity between 5 -11 years of age. Mating can occur at any time of the year, but generally happens during the 3-5 month mating season when they make the southward migration. Pregnant females tend to lead the migration. Courtship and mating behaviors is complex with these whales and there is general three or more whales involved in the mating process.

Gestation for these whales lasts for 12-13 months. When the calf is born it is dark gray, weighing approximately 1,100 - 1,500 pounds and is about 15 feet in length. These calves will be nursed for 7-8 months on milk that is 53 percent fat. Once they have reach 7 months the mother will begin showing them how to feed otherwise.

The average lifespan of a gray whale is 50 years. However, it has been recorded that they can live to be 77 years of age. This is quite rare though.

Taxonomy

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Cetacea

Family: Eschrichtiidae

Genus:Eschrichtius

Species:robustus

Social Structure

Gray whales travel in small pods of three to sixteen. During feeding season it may appear to be more whales to a pod, however, it is just several pods feeding in the same area. In fact, although they travel by pods, gray whales do not for lasting relationships.

Gray whales have been known to approach boats in lagoons, allowing humans to touch them. The reason is unclear and is still quite the debate. Some people think that the reason is because they are simply curious while other believe that they are assessing whether the boats will be a threat to their young.

Vocalization

Gray whales have songs that sound more like grunts, clicks, and whistling sounds. It is believed that this is mainly for communicating with other gray whales in the area. To hear a sound clip of a gray whale, go to the National Geographic website.

Habitat

Although they have been spotted in the Arctic Ocean and the Northern Atlantic Ocean, these whales mostly inhabit the waters of the Pacific Ocean. Most of the sightings have been along the North American Coast. Each year the gray whale will migrate to the lagoons of Mexico to breed and give birth. This usually takes about 2-3 months to get there. Then they will migrate north again when it time to return to their summer feeding grounds.

Diet

The gray whale is a seasonal feeder. They rarely eat outside the summer months. Because the gray whale is a baleen whale, it tends to feed on crustaceans such as crab, shrimp, lobsters, and barnacles. They also feed on squid, fish, and plankton.

In order for this magnificent whale to feed, it will dive to the bottom. Then it will roll on its right side to take in bottom sediments and water into its mouth. As the gray whale closes its mouth, water and sediment is filtered through the baleen leaving only food in its mouth. It will then use its tongue to loosen any food caught in the baleen and then swallows its food whole.

Conservation

The IUCN has listed the gray whale's conservation status as "least concern". However, the IUCN has accessed the western gray whale separately and consider them to be "critically endangered".

The biggest threat to these whales is whaling. Although they are supposed to be protected by the Marine Mammal Protection Act, the International Whaling Commission still allows certain countries to continue whaling. These countries include Norway, Iceland and Japan and the aboriginal communities of Siberia, and northern Canada as well as the Alaskan coast in the United States.

Pollution is another threat to the gray whales. It poisons their food supply and thus poisons the milk produced that is fed to the calves. Many whales fall victim to this senseless act.

If you would like to adopt a gray whale, you can visit CascadiaResearch.org for more information. By adopting a gray whale, you will be helping to contribute to research and conservation of gray whales.